High power electron tube apparatus



March 1968 A. 0. LA RUE 3,374,523

HIGH POWER ELECTRON TUBE APPARATUS Original Filed Jul 31, 1963 3 Sheets-Sheet l INVENTOR. ALBERT D. LA RUE h n v BY/fl l 7 ATTORNEY March 26, 1968 A. D. LA RUE 3,374,523

HIGH POWER ELECTRON TUBE APPARATUS Original Filed July 31, 1963 5 Sheets-Sheet 2 FIG. 3

INVENTOR. ALBERT D. LA RUE I ATTORNEY March 26, 1968 A. D. LA RUE HIGH POWER ELECTRON TUBE APPARATUS 3 Sheets-Sheet 5 Original Filed July 31, 1963 FIG. 5

84 FIG.8

INVENTOR. ALBERT D. LA RUE M ATTORNEY United States Patent C) 3,374,523 HIGH POWER ELECTRON TUBE APPARATUS Albert D. La Rue, Los Altos, Calif., assignor to Varian Associates, Palo Alto, Calif., a corporation of California Continuation of application Ser. No. 299,001, July 31, 1963. This application Nov. 16, 1956, Ser. No. 595,309 2 Claims. (Cl. 29-1573) ABSTRACT OF THE DISCLOSURE A collector assembly for large high power electron tubes such as klystrons. The collector assembly is formed of simple geometrical sections such as cones and cylinders brazed together at their edges. Each of the sections is formed by rolling a composite sheet comprising a layer of stainless steel brazed to a layer of copper, into the abutting side of which fiuid coolant passages have been formed.

This invention is a continuation of application Ser. No. 299,001, filed July 31, 1963.

This invention relates generally to a high power electron tube apparatus and more particularly to a collector assembly for high power electron tube apparatus and method of manufacturing the same.

In high or super power electron tube apparatus employing electron beams, the collector for the beam is made relatively large in comparison to the beam diameter so that the high power of the beam can be dissipated over a large collector surface area.

By way of example, if such a tube has a peak power output in the order of megawatts or more and an average power output of 100 kilowatts or more, the beam power in the tube may be three times this value. The collector must be capable of handling this high power. Arbitrarily, the collector must be a heat exchange device capable of handling three megawatts of peak power and 300 kilowatts of average power for the smallest super power tubes. A number of tube applications now exist in which the power requirements greatly exceed these values and thus power dissipation from the collector is even more important.

An electron tube of the foregoing character may include a cylindrical collector which is 1 to 3 feet in diameter and from 2 to 6 feet in length. The fabrication and assembly of such a collector presents many problems. With the conventional design and lower powers, for example, the main body of the collector may be machined from a single piece of copper. In the higher power tubes such as those discussed above, the fabrication of the collector requires a more sophisticated technique. One method has been to manufacture the large parts required from sheet material, by a succession of deep drawing and machining operations, to form the basic parts. Successive brazing and hand fitting operations are then required to complete the assembly. The assembly may include a main collector body with an outer body sealed thereto to define with the collector a cooling jacket through which a coolant may be circulated to convey away the heat. The large dimensions of the parts, however, make it diflicult to obtain satisfactory fits for brazing. The large pieces being brazed make it difficult to maintain the substantially constant temperature required for satisfactory brazing.

Furthermore, a water or liquid cooled collector must also be adaptable to the particular system in which it is used. In most systems, the design might dictate a pressure drop of the cooling fluid such as not to exceed 70 p.s.i.g. at a coolant temperature rise not to exceed 20 C. The coolant temperature rise permitted and the heat transfer constant obtained in the collector design determines the power that may be handled per unit collector area. This fixes at least the minimum collector size. However, con ditions are not ideal. For example, the electron beam of the apparatus may not be evenly distributed over the collector surface area. Thus, the collector assembly must be capable of dissipating substantially greater amounts of power per square inch than the theoretical power in order to avoid burnout.

It is a general object of the present invention to provide an improved collector assembly for high power electron devices.

It is a further object of the present invention to provide a bimetal collector which provides good heat dissipating characteristics and high mechanical strength.

It is a further object of the present invention to provide a collector made of sheets of different material joined together to define passages for the cooling medium.

It is a further object of the present invention to provide a collector made of two metals, one of which pro vides high heat conductivity and the other of which pro vides high strength to the collector so that the collector may form a portion of the tube envelope and sustain the large atmospheric pressures to which it is subjected because of the large size required to provide suflicient surface area for power dissipation.

It is a further object of the present invention to provide a collector which is formed by rolling a preassembled fiat bimetal assembly.

It is a further object of the present invention to provide a collector assembly which is simple in construction and effective to dissipate large amounts of power.

It is a further object of the present invention to provide a collector assembly which is simple and easy to manufacture.

It is a further object of the present invention to provide a collector formed by vacuum brazing large fiat sheets of material together and then forming the assembly into cylinders and cones joined to one another to define the collector assembly.

It is a further object of the present invention to provide a bnnetal collector in which a grooved high conductivity good vacuum characteristics sheet, such as copper, has brazed thereto a high strength flat sheet of material, such as stainless steel, to form a multitude of coolant passages.

It is a further object of the present invention to provide an improved method for fabricating a collector for high power electron tube apparatus.

The foregoing and other objects of the invention will become more clearly understood from the following description taken in conjunction with the accompanying drawings.

Referring to the drawing:

FIGURE 1 is a longitudinal foreshortened view, partially in section, of a high power electron tube apparatus incorporating a collector in accordance with the present invention;

FIGURE 2 is a top view of the electron tube apparatus;

FIGURE 3 is an enlarged view, partly in section, of the collector taken generally along the line 33 of FIG- URE 1;

FIGURE 4 is an enlarged view of a portion of the collector taken generally along the line 44 of FIGURE 1;

FIGURE 5 is a plan view of the groove configuration of the rectangular sheet used to form the cylindrical collector portion;

FIGURE 6 is a plan view of the grooves employed in the assembly for forming the cone portion of the collector;

FIGURE 7 is a plan view showing the grooves in the portion used to form the fiat top of the collector; and

3 FIGURE 8 schematically illustrates a method of forming the bimetal structure used in construction of the envelope.

Referring to FIGURE 1, there is shown a high power electron tube apparatus, namely a klystron, incorporating the tube envelope and serves to form and project a beam of electrons over a predetermined path directed axially and longitudinally of the envelope -1 in cooperative relationship with the interaction structure disposed along the envelope to support the electromagnetic energy. The collector structure 5 is disposed at the other end of the envelope to collect the electron beam. A coolant as, for example, water, is circulated through suitable ducts formed in the collector structure 5 to be presently described in detail through the manifolds 6 which are provided with fittings 7.

A plurality of reentrant cavity resonators are disposed along the envelope and form the interaction structure. The input and output resonators 8 and 9 are arranged along the beam path in axially spaced relationship so that the electromagnetic energy can interact with the beam passing therethrough. Input wave energy to be amplified is applied to the input resonator 8 via the input loop 10 and coaxial line 11. Amplified output wave energy is extracted in a conventional manner through the output resonator 9 and propagated to a suitable load (not shown) via the output wave guide 12 sealed in a vacuumtight manner by means of a wave-permeable vacuumtight window (not shown). Axially movable tuning structures 13 are disposed within the cavity resonators 8 and 9 respectively for tuning the tube over the operating frequency range.

A solenoid 14 coaxially surrounds the elongated vacuum envelope 1 and provides an axially directed beam focusing magnetic field as, for example, a field having a strength of 1000 gauss. The magnetic field confines the beam to a predetermined beam diameter and directs the same axially along the tube. A hollow cylindrical magnetic shield 15, as of soft iron, surrounds the solenoid for minimizing leakage of the magnetic field. At the gun end of the tube 1, the shield 15 abuts an aperture plate 16, as of soft metal, forming the top of an iron tank containing an oil bath 17 in which the gun end of the tube, including the solenoid 14, is immersed. The iron of the tank forms a portion of the magnetic shield. The oil bath having a dielectric strength greater than air reduces the probability of are across the insulators of the gun strucrum .4.

In operation, input signals are applied to the input resonator at the coaxial line 11, the signals are amplified in successive resonators and an amplified output signal is recovered from the tube at the waveguide 12.

A typical tube may utilize a beam voltage in the order of 140 kilovolts and a beam current in the order of 100 amperes with an average power in the order of megawatts to produce hundreds of kilowatts of average and megawatts of peak ultra-high frequency output power.

In such power tubes, as previously described, with the average beam power being of megawatts or more, the energy of the beam entering the collector must be dissipated and carried away or the collector will burnout due to the high heat generation.

In accordance with the present invention, there is .provided an improved collector structure which includes as its wall one or more bimetal plates which have formed therein passages for the transfer of coolant. The collector includes an outer shell which provides strength to the transfer to the coolant.

The coolant is introduced at the fitting 7 and travels into a manifold 6 which provides communication with a plurality of openings formed in the bimetal cylindrical portion of the collector to be presently described in detail. Referring to FIGURES 1'4, the collector assembly comprises a bimetal cylindrical body portion 21 including a first grooved metal plate 22 which has brazed thereto a metal plate 23. As will be presently described in detail, the metal 22, a soft metal having good electrical and vacuum properties such as copper, is grooved with a plurality of grooves 24 which form lands 26. The outer cover sheet 23 may be formed of stainless steel and suitably brazed to the lands. The structure provides a surface for collecting the electrons having good electron and heat conducting characteristics, while the outer shell or plate 23 provides strength to the collector to withstand the high atmospheric pressures at the outside of the cylindrical collector structure due to the vacuum within the same.

Cooperating with the drift tube 27 is a truncated conical portion of the collector structure 28 likewise formed from a bimetal plate including a plurality of coolant passages. The outer end of the collector structure is formed by a truncated conical portion 29 likewise formed of a bimetal'plate defining coolant passages 24 and having its lower end suitably sealed to the adjacent portion of the cylindrical portion 21. The upper end of the conical portion 29 receives a fiat cover 31 likewise formed from a bimetal plate including fluid passages 24.

The passages 24 are generally formed as parallel circumferentially running passages. Means are provided for fluid communicating with predetermined ones of said pas sages for forming an inlet to the coolant passages and spaced means are provided for forming an outlet. The inlet and outlet connections may be holes machined into the outer shell 23 in communication with predetermined passages in such a manner as to provide parallel flow of fluid between the inlet and outlet. This provides a large volume of fluid flow with minimal pressure drops.

The fluid is provided to the inlet passages through a manifold '6 which is provided with an inlet fitting 7. The manifold includes a tapered portion at the upper conical section and a pipe 37 provides suitable communication between this portion and the upper plate.

Fluid is removed from the collector structure 'by a piping and manifold arrangement similar to that described and including manifold portions 41 and 42, pipes 44 and 46, and a fitting 4 7. Suitable fluid connection (not shown) is made with the coolant passages 24 of the lower cone 28.

As just described, the flo'w is a substantially parallel flow which, in essence, forms a sheath of coolant flowing circumferentially around the collector. This is indicated generally by the arrows 48 in FIGURE 3.

Referring to FIGURE 5, there is shown the grooved plate 22 which may be used to form a portion or the assembly employed to fabricate the cylindrical portion 21 of the collector. It is observed that the grooved plate 22 includes a plurality of continuous channels 52 which define a plurality of lands 53. Each channel is formed as a continuous closed channel. For example, observing the channel 52, it is seen that it is closed upon itself. Predetermined spaced lands are cut as shown at 53 to provide communication between adjacent continuous channels. The lands are cut at a spacing such that fluid introduced, for example, in the channels 52, will flow as shown by the various arrows 54 in both directions. Tracing the flow of this fluid, it is seen that it flows along the respective channels to both ends 56 and 57 of the same land 53, and back to where it finds slots 59 formed in another land. The fluid can then flow outwardly into an outlet manifold disposed adjacent these slots.

The grooved plate is covered with the other sheet of metal 23 and the assembly is suitably brazed. A plurality of openings 61 are provided in the sheet 23 to communicate with the underlying inlet slots 58 and the outlet slots 59.

It is observed that all coolant flows substantially the same distance through the structure and that, in essence, there is a sheath or blanket of water moving circumterentially in parallel streams to provide large volume flow with minimum pressure drop.

The cones may be formed from a flat piece of material which is in the form of a disc having a cut-out portion such as that shown in FIGURE 6. Again, the grooves 62 are formed as continuous grooves. The inlet connections are provided by ports arranged adjacent the slotted portion 63 of the grooves 62 and the outlet ports are arranged adjacent the slotted portions 64 of the grooves. Fluid then flows through the channels in parallel streams.

In FIGURE 7, there is shown a typical configuration of the grooved plate for the top cover of the collector. Again, the grooves 72 are so arranged that the fluid flows in parallel paths across the structure to form a sheath of cooling fluid. The inlet port is arranged at the region designated generally by the numeral 73 and the outlet port in the region 74.

The bimetal structures are formed as fiat plates and then shaped as desired to form the collector. Referring to FIGURE 8, there is schematically shown a method of forming the flat bimetal plates. The soft metal plate 22 is grooved to form lands. A brazing compound is placed on the lands and then the cover sheet 23 is placed on the lands. A pair of assemblies may be placed back to back as shown in FIGURE 8 and the entire structure enclosed in an envelope having a flat top sheet 81 and bottom sheet 82 with side walls 83 and 84. An outlet port 86 is provided for attaching a vacuum pump thereto. The assembly is then evacuated and the atmospheric pressure on the outside presses in and applies suitable pressure to the a high temperature furnace to provide a competent braze whereby the cover sheets 23 are brazed to each of the lands to form the 'bimetal structure previously described.

Since many changes could be made in the above construction and many apparently widely difierent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. The method of forming a collector for electron tube apparatus which comprises the steps of, forming a first metal sheet having good heat conductivity to provide a plurality of elongated adjacent grooves defining therebetween lands on one side of said sheet, the other side of said sheet being smooth, placing a second metal sheet having good mechanical strength in contact with said lands, applying pressure between the first and second sheets, vacuum brazing said second sheet to said lands under the applied pressure to provide an assembly defining with said grooves a plurality of coolant passages, forming spaced inlet and outlet openings in the assembly and communicating with predetermined ones of said passages, forming said assembly into the shape of the collector with the second sheet forming the exterior, and joining the side margins of said assembly to complete an envelope of the collector.

2. The method of claim 1 wherein said first metal sheet is of copper and the second metal sheet is of steel.

References Cited UNITED STATES PATENTS 2,568,653 9/1951 Majonnier 29--157 X 2,995,807 8/ 1961 Gibbs 29-1573 3,091,846 6/ 1962 Henry 29-494 X 3,227,904 1/ 1966 Levin 313-21 WILLIAM I. BROOKS. Primary Examiner. 

